import math
x1,y1,x2,y2 = map(float,input().split())

x_d = x2 - x1
y_d = y2 - y1
print("%0.5f" % math.sqrt(x_d**2 + y_d**2)) import math math x1,y1,x2,y2 = map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 x_d = x2 - x1 x_d x2 - x1 x2 x1 y_d = y2 - y1 y_d y2 - y1 y2 y1 print("%0.5f" % math.sqrt(x_d**2 + y_d**2)) print "%0.5f" % math.sqrt(x_d**2 + y_d**2) "%0.5f" math.sqrt(x_d**2 + y_d**2) math.sqrt math sqrt x_d**2 + y_d**2 x_d**2 x_d 2 y_d**2 y_d 2 x2,y2 = map(float,input().split()) map(float,input().split()) x2 x1,y1,x2,y2 = map(float,input().split()) map(float,input().split()) x1 y1,x2,y2 = map(float,input().split()) map(float,input().split()) y1 y2 = map(float,input().split()) map(float,input().split()) y2 y_d = y2 - y1 y2 - y1 y_d x_d = x2 - x1 x2 - x1 x_d
import math
x1,y1,x2,y2 = map(float,input().split())

x_d = x2 - x1
y_d = y2 - y1
print("%0.5f" % math.sqrt(x_d**2 + y_d**2))